| At a glance | Acute crystal arthritis from calcium pyrophosphate deposition; classic site is the knee with chondrocalcinosis. | Bacterial infection of a joint — orthopedic emergency requiring urgent arthrocentesis and drainage. |
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| Classic presentation | Acute monoarticular or oligoarticular swelling, pain, and warmth — most often knee or wrist; Onset over hours to a day; often precipitated by surgery, trauma, or acute medical illness; Less severe than typical gout but can be incapacitating; Chronic forms: insidious polyarticular arthritis mimicking RA or OA; Warm, swollen joint with… | Acute monoarticular pain, swelling, warmth, erythema; Markedly reduced range of motion; Fever, chills (variable — fever absent in up to 40%); Migratory polyarthralgia, tenosynovitis, and pustular rash suggest disseminated gonococcal infection; Joint effusion with warmth and erythema; Extreme pain on passive motion (vs bursitis where… |
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| Workup / key labs | ACR/EULAR 2023 classification criteria for CPPD use clinical features + imaging + crystal identification.; Arthrocentesis with polarized microscopy — rhomboid or rod-shaped, POSITIVELY birefringent CPP crystals; inflammatory fluid; Gram stain and culture to exclude septic arthritis; Screen for underlying metabolic disease in patients… | Arthrocentesis BEFORE antibiotics when possible (do not delay antibiotics if patient septic):; • WBC count, differential (typically >50,000 with >75% PMNs; gonococcal often lower); • Gram stain (sensitivity ~50%); • Bacterial culture (aerobic and anaerobic); • Crystals on polarized microscopy; Blood cultures × 2 sets (positive in ~50%);… |
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| Imaging | Plain radiographs — linear calcification within hyaline or fibrocartilage (chondrocalcinosis), classically in knee menisci, triangular fibrocartilage complex of wrist, symphysis pubis; Ultrasound — hyperechoic deposits within cartilage; DECT — less established than for gout | Plain radiographs — baseline; usually unremarkable acutely; soft tissue swelling, joint effusion; Ultrasound — guides aspiration, especially for deep joints (hip); MRI — if osteomyelitis suspected or to evaluate axial joints (SI, sternoclavicular) |
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| First-line treatment | Acute flare: Intra-articular corticosteroid injection (triamcinolone 40 mg) — preferred when septic excluded, especially for knee; Acute flare: Oral NSAIDs — ibuprofen, naproxen, indomethacin (full anti-inflammatory dose, short course); Acute flare: Colchicine 1.2 mg, then 0.6 mg one hour later, then 0.6 mg BID-TID; Acute flare:… | Empiric antibiotics: Vancomycin to cover MRSA (or daptomycin/linezolid if vancomycin contraindicated); Empiric antibiotics: Add gram-negative coverage based on host: ceftriaxone (community), cefepime or pip-tazo (immunocompromised, healthcare-associated); Empiric antibiotics: Sexually active young adult with disseminated features:… |
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